Raman and ROA Spectra of (−)- and (+)-2-Br-Hexahelicene: Experimental and DFT Studies of a π‑Conjugated Chiral System
Articolo
Data di Pubblicazione:
2013
Abstract:
The Raman optical activity (ROA) spectra of both enantiomers of 2-Brhexahelicene
in chloroform solution have been measured in the range 1700−300 cm−1.
Density functional theory (DFT) calculations accurately reproduce the observed features.
The most intense ROA features are also the most intense Raman features, in the region
1350−1400 cm−1, and correspond to the so-called D-modes, which play a major role in
coronene and other PAHs (polycyclic aromatic hydrocarbons). Together with a detailed
analysis of the normal mode structure, the polarizability tensors for the intense Raman
features are investigated and related to the principal characteristics of helicene systems,
namely, chirality and π-conjugation. Through electron−phonon coupling analysis, we
propose a mechanism that justifies the intense ROA signals.
in chloroform solution have been measured in the range 1700−300 cm−1.
Density functional theory (DFT) calculations accurately reproduce the observed features.
The most intense ROA features are also the most intense Raman features, in the region
1350−1400 cm−1, and correspond to the so-called D-modes, which play a major role in
coronene and other PAHs (polycyclic aromatic hydrocarbons). Together with a detailed
analysis of the normal mode structure, the polarizability tensors for the intense Raman
features are investigated and related to the principal characteristics of helicene systems,
namely, chirality and π-conjugation. Through electron−phonon coupling analysis, we
propose a mechanism that justifies the intense ROA signals.
Tipologia CRIS:
1.1 Articolo in rivista
Elenco autori:
Johannessen, C.; B. l. a. n. c. h. E., W.; Villani, C.; Abbate, Sergio; Longhi, Giovanna; Agarwal, N. R.; Tommasini, M.; Lightner, D. A.
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